1. Field of the Invention
This invention relates to apparatus for reproducing a digital signal and, more particularly, to novel and highly-effective apparatus for reproducing a digital signal recorded on a tape by a rotary head.
2. Description of the Prior Art
Apparatus for recording and reproducing a digital signal is known, in which an analog signal such as an audio signal or the like is converted to a digital signal; a digital signal indicative of an address, a program number and the like together with the converted digital signal is recorded by a rotary head on a tape that is transported at a normal speed; the digital signal thus recorded is reproduced from the tape transported at the normal speed; the reproduced digital signal is converted to an analog signal such as an audio signal; and the recorded address, program number and the like are confirmed. For example, European patent application Ser. No. 0092403, filed by the assignee of the present application and published on Oct. 26, 1983, discloses such apparatus for recording and reproducing a digital signal. In the conventional recording apparatus, it is required that, even when the tape is transported at a high speed, a part of the digital signal such as an address signal and program number recorded on the tape be reproduced by the rotary head to confirm the position of the information recorded on the tape and to control the operation of the tape. However, when the tape is transported at high speed, if the rotary head is rotated at the normal speed, the relative speed between the tape and the head becomes different from that in the normal playback mode. Thus it becomes difficult to reproduce the digital signal recorded on the tape.
Copending U.S. patent application Ser. No. 06/791,518, filed on Oct. 25, 1985, by the assignee of the present application, discloses apparatus for reproducing a digital signal recorded on a tape, the apparatus including means for controlling the relative speed between the tape and a rotary head to become substantially the same as that in the normal playback mode, even when the tape runs at high speed. In the aforesaid apparatus, when the relative speed between the tape and the rotary head deviates significantly, the rotation of the rotary head is controlled in response to the maximum transition interval of the reproduced digital signal. In this case, however, if a drop-out occurs in the reproduced signal because of dust, scratches and the like on the tape, the accuracy of the control of the rotation of the rotary head is diminished.